1. Field of the Invention
This invention relates to a means controlling the tilt of a display unit screen, and, more particularly, for releasably locking a screen of a touchscreen display unit at an adjustable tilt angle.
2. Description of the Related Art
In the patent art, a number of examples are found of mechanisms for controlling the tilt of a computer display through the use of one or more spring clutches or brakes arranged to resist a downward tilting movement of the display while releasing the display to be tilted upward. These mechanisms do not include means for releasing the clutch or brake to allow free downward tilting movement of the display; the clutches or brakes must be overpowered in order to tilt the display downward.
An example of such a mechanism is found in U.S. Pat. No. 5,771,152, which describes a tilt adjustment mechanism having an upper housing, a lower housing, and a shaft assembly. The shaft assembly receives gears which are pressed on either end of the shaft, which fits through locating slots in the lower housing. Each of the gears is activated by internal gears located on each side of the upper housing and integrally formed with the upper housing. The upper housing is hinged on the lower housing and can rotate 20 degrees. The shaft assembly mechanism provides a torsion bar function to insure that the upper housing moves evenly with respect to the lower housing. The shaft assembly mechanism decouples the frictional load in the two different rotational directions about its shaft, permitting adjustment of the forces to optimal levels in both directions. This mechanism includes a one-way clutch, in the form of a spring clutch or a bearing clutch, operating between the shaft and a bushing held within a clamp. When the upper housing is raised, the clutch releases to permit rotation of the shaft. When the upper housing is lowered, the clutch locks the shaft to the bushing, which then rotates within the clamp, with friction between the bushing and the clamp significantly increasing the force required to lower the upper housing.
Another example of such a mechanism is found in U.S. Pat. No. 5,206,790, which describes a laptop computer in which a display is connected to the lower housing by a pivot mechanism and a swivel mechanism. In the pivot mechanism, a pivot connects the display to a pivot plate, and a second pivot connects the pivot plate to the lower housing. The pivot consists of a pivot pin on each end of the pivot plate. The second pivot consists of split pivot pins at each end of the pivot plate. Each of the split pivot pins includes a pivot pin connected to the pivot plate and to an extension shaft having a sleeve portion extending over the end of the pivot pin and a shaft portion extending, and turning within a sleeve attached to the lower housing. A clutch spring extending over the sleeve and the sleeve portion of the extension shaft is arranged to unwind, releasing its connection between the sleeve and the extension shaft, as the display is opened, but to wind tighter, establishing a friction connection between the sleeve and the extension shaft, as the display is closed.
U.S. Pat. No. 5,197,704 also describes the use of spring clutches in a tilt adjusting mechanism for a display device. The angle adjusting device has a stationary bracket to be attached to a base and a rotating bracket to be attached to the display device. Each of these brackets is attached to a sleeve extending inward from the bracket. A shaft, having ends extending within the sleeves, also has an enlarged central portion extending between these sleeves. At each end of this enlarged central portion, a clutch spring extending over a part of the enlarged central portion and over the adjacent sleeve resists relative rotation between the shaft and the adjacent sleeve.
U.S. Pat. No. 5,173,837 describes the use of a clutch spring, through which a hinge pin for a laptop computer display extends, within a bracket in which the pin is pivotally mounted. The opposite ends of the clutch spring extend over a portion of the bracket to hold the spring in place. This arrangement produces approximately the same drag torque when the display is opened as when it is closed.
Other examples of the patent literature describe ways to provide friction at the pivot of a computer display through the use of friction braking without spring clutches. For example, U.S. Pat. No. 5,913,351 describes the use of friction plates held together on a pivot screw by means of a spring washer. U.S. Pat. No. 5,638,579 describes the use of a pair of bronze bearing blocks, one of which is responsive to precisely applied compressive force to produce user-controllable amounts of static and rotational friction to the tilt axis. U.S. Pat. No. 5,924,665 describes a multi-jointed and pivoted ceiling system for mounting a flat panel video display, employing elevational pivot assemblies including plastic friction washers and gas springs.
A problem common to these prior-art devices is that they fail to provide a release mechanism for disengaging the clutch or brake applying the friction torque. Thus, to move the display at least in one direction, a force sufficient to overcome the friction torque must be applied. In many applications, this friction torque must be substantial because it must be sufficient to hold the display in place when it is located so that gravity applies a maximum torque trying to lower the display. Having to overcome this friction torque makes it difficult to move the display and to position it precisely at a desired angle. As the display is manually moved against the friction torque, various parts within the display and within the mechanism through which it is mounted deflect elastically. When the torque moving the display is released, these elastic deflections are removed, so that the display does not remain where it has been positioned.
Thus, what is needed is a mechanism applying a drag torque to a computer display as it is tilted, with the mechanism including releasing means operable to cause the drag torque to be removed so that the display can be freely tilted in both directions.
Accordingly, it is a first objective of the present invention to provide a braking mechanism, for restraining the tilting of a display housing, including a mechanism for releasing the braking mechanism to allow free movement of the display housing.
It is a second objective of the present invention to provide a braking mechanism which restrains the tilting of a display housing in both directions.
It is a third objective of the present invention to provide a braking mechanism, for restraining the tilting of a display housing, through which the display housing is rigidly held.
According to a first aspect of the present invention, there is provided a display unit including a base, an upper housing having a display screen, a pivot shaft, a first brake, and manually operated release means. The pivot shaft pivotally mounts the upper housing on the base. Pivoting the upper housing about the pivot shaft changes an angle of tilt of the display screen relative to the base. The first brake restrains pivoting of the upper housing in a first direction. The manually operated release means causes the first brake to release, allowing pivoting of the upper housing in the upper direction.
According to a second aspect of the present invention, there is provided apparatus for pivotally mounting an upper housing, including a display screen, on a base within a display unit. Pivoting the upper housing within the apparatus changes an angle of tilt of the display screen relative to the base. The apparatus includes first and second brakes. The first brake includes a first stator rigidly attached to a first end of the base and a first rotor rigidly attached to a first end of the upper housing, wherein the first rotor is pivotally mounted on the first stator, being restrained from rotation when the first brake is engaged, and being free to rotate when the first break is released. The second brake includes a second stator rigidly attached to a second end of the base, opposite the first end of the base, and a second rotor rigidly attached to a second end of the upper housing, opposite the first end of the upper housing, wherein the second rotor is pivotally mounted on the second stator, being restrained from rotation when the second brake is engaged, and being free to rotate when the second break is released, and wherein the first and second rotors are aligned along a common axis of rotation.